Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017
Operating activities
Net loss	$ (63,436)		$ (74,453)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	2,005		1,965
Amortization of deferred financing costs	144		360
Amortization of deferred compensation for services	177		142
Amortization of premium on investment securities	(708)		57
Stock-based compensation	6,976		7,001
Change in derivative liabilities	56
Non-cash interest expense relating to loan payable	164
Changes in operating assets and liabilities:
Accounts receivable	10,629
Prepaid expenses and other assets	(3,908)		(2,178)
Accounts payable	(1,609)		(3,182)
Accrued compensation and benefits	(923)		(439)
Accrued and other liabilities	(1,405)		839
Net cash used in operating activities	(51,838)		(69,888)
Investing activities
Proceeds from maturities of investments	95,450		109,923
Sales and redemptions of investments	850		16,857
Purchases of investments	(148,360)		(70,384)
Purchases of property and equipment	(24)		(2,327)
Net cash (used in) provided by investing activities	(52,084)		54,069
Financing activities
Proceeds from loan payable, net of issuance costs	49,292
Proceeds from underwritten public offering, net of issuance costs	53,770
Proceeds from issuance of common stock under stock plans	492		675
Net cash provided by financing activities	103,554		675
Net decrease in cash and cash equivalents	(368)		(15,144)
Cash and cash equivalents at beginning of period	75,383	[1]	74,598
Cash and cash equivalents at end of period	75,015		$ 59,454
Supplementary disclosure of non-cash financing information:
Issuance of derivative in connection with issuance of loan payable	$ 546

[1] Derived from the audited consolidated financial statements included in the Company’s Annual Report on Form 10K for the year ended December 31, 2017.